DS Question

Expert replies

Previous Topic Next Topic

jogi1984: Junior | Next Rank: 30 Posts; Posts: 14; Joined: Wed Mar 30, 2011 7:36 am

by jogi1984 » Thu Sep 15, 2011 8:01 pm

If (243)x(463)y = n, where x and y are positive integers, what is the units digit of n?

(1) x + y = 7

(2) x = 4

Like this post

Source: Beat The GMAT — Data Sufficiency | Thu Sep 15, 2011 8:01 pm

cans: Legendary Member; Posts: 1309; Joined: Mon Apr 04, 2011 5:34 amFollowed by: 123 members; Location: India; Thanked: 310 times; GMAT Score:750

by cans » Thu Sep 15, 2011 8:57 pm

(243)^x* (463)^y = n
x+y=7 sufficient. unit digit is 7.
x=4 insufficient. y not known.
IMO A

If my post helped you- let me know by pushing the thanks button

Contact me about long distance tutoring!
[email protected]

Cans!!

Like this post

jogi1984: Junior | Next Rank: 30 Posts; Posts: 14; Joined: Wed Mar 30, 2011 7:36 am

by jogi1984 » Thu Sep 15, 2011 9:19 pm

Hi Cans,
Thanks a lot...
but how to go for it ..Does 463 have sm factors of 3 ???

Like this post

1947: Master | Next Rank: 500 Posts; Posts: 215; Joined: Sat Jun 14, 2008 4:24 pmFollowed by: 1 member; Thanked: 13 times

by 1947 » Sat Sep 17, 2011 1:36 am

(243)^x* (463)^y = n
x+y=7 sufficient. unit digit is 7.

3^x repeats like 3,9,27,81,243 i.e. after every 4 powers unit digit is 3.
243 = 3^5
since 243 also ends with 3 so if 243 has any factor of 3 becomes meaningless...
what question is asking is what is the unit digit of 3^(x+y)
since x+y = 7 we can find the unit digit.
let me know if it explains

If my post helped you- let me know by pushing the thanks button. Thanks

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

560 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (560 Reviews)

"Target Test Prep is the closest to the official version of the GMAT exam, about 99% accuracy in terms of the quality and quantity of information. The course has excellently created singular sets of focused lessons and tests for every possible topic that one could come across in the official GMAT exam."

"The TTP course maximizes the efficiency of the time you spend studying. It will take time and effort but I could almost guarantee that if you complete the course exactly as it is laid out you will get an amazing score. They also have a very responsive team willing to help with any questions you might have."

"TTP has two things that I think no other test prep company offers: A teaching approach that reinforces understanding and an attitude that will give you the mental preparedness needed to succeed on the test. TTP gives you a deep understanding of the concept you need to know while teaching you how to think."

Write a Review